1. Field of the Invention
The present invention relates to an improved process in drilling for hydrocarbons, whereby permeable zones are detected as soon as they are penetrated, using the Supercharger Process, and whereby the Supercharger Tool is actuated into a conventional drilling mode to stop the potential influx of down hole fluids. After the permeable zone has been penetrated, the invention allows the tool to be converted back to the Supercharger process to allow further increases in rate of penetration.
2. General Background of the Invention
U.S. Pat. No. 4,633,958 ('958 patent), entitled “Downhole Fluid Supercharger,” which is incorporated by reference herein, describes a process whereby high velocity (supercharged) streams of drilling fluid are directed upward on an intermittent basis to increase rates of penetration in drilling operations. These penetration rates are increased because hydrostatic pressure acting on the bottom of the hole is intermittently reduced due to the resultant low pressure of the high velocity streams.
The Supercharger Process can be accurately described as claim 20 in the '958 patent as the method described as follows: “. . . wherein the steps of interrupting and resuming the fluid flow to said drill bit are repeated during cyclical rotations of said drill string . . .”
It should be mentioned for clarity that “interrupting and resuming the fluid flow to said drill bit” as described in the '958 Patent consists of two parts, the “functioning of the apparatus between the first position for jetting and diffusing exterior to the apparatus and a second position to blocking such jetting and diffusing and allowing fluid flow to the bit”. Typically the first cycle (jetting and diffusion) is called the Supercharger Cycle, and the second position (flow to the bit) is called the Drilling Cycle.
As described in the '958 Patent, it is imperative that the Supercharger Cycle is regularly interrupted by the Drilling Cycle in order to remove cuttings generated by the drill bit from below the tool to above tool. If this is not done on a cyclical basis, cuttings will build up below the tool and ultimately cause the tool to get stuck in the hole, as the Supercharger Cycle effectively blocks the annulus between the tool and borehole wall to enable pressure reduction at the bit, which disallows the passage of cuttings. The Drilling Cycle allows unobstructed passage of cuttings around the tool, with fluid flow exiting the bit in a conventional manner.
The '958 Patent describes an apparatus that continuously cycles in a three to one rotation of the drillstring from the Supercharger Cycle to the Drilling Cycle; hereinafter called the Supercharger Tool; however, no provisions were made to be able to detect permeable zones, and lock the tool into a continuous, conventional Drilling Cycle so that permeable zones can be safely penetrated without allowing an influx into the well.
A decrease in pressure and corresponding increase in drilling rates are well documented. A technique called Under Balanced Drilling is widely used in industry to exploit the efficiency of low pressure drilling. This technique lowers the entire pressure throughout the well bore by utilizing low density fluids and capping the top of the well with a sealing rotating device called a “rotating head”. This device contains hydrocarbons that may enter the well bore due to the lowered pressure, thereby preventing an uncontrolled flow or “blowout”. Separation equipment is installed on the surface and removes hydrocarbons from the drilling fluid as well as utilizing a combustible flare to dispose of these potentially dangerous substances.
It should be mentioned that the above technique is employed in “tight” formations such that the magnitude of influxes is relatively small. In high permeability formation, such as encountered offshore, the Under Balanced Drilling technique is not generally utilized due to safety concerns.
It will be shown that such extraneous equipment and associated dangers are not required to achieve the same results of increased rates of penetration with the present invention, particularly in offshore operations where high permeable formations are routinely encountered.
U.S. Pat. No. 4,633,958 does not address the potential of hydrocarbons entering the well bore below the tool due to the lowered pressure below the tool that is allowed on an intermittent basis. Therefore, the method described in the Patent does not provide a safe means of utilizing the Supercharger Process; if a permeable, hydrocarbon-bearing zone is penetrated with the tool, hydrocarbons can enter the well bore, resulting in a “well control” situation, whereby time-consuming and relatively dangerous techniques are required to seal the well, circulate the influx of hydrocarbons and remove them from the drilling fluid.